This invention relates to a method and system for fuel delivery that limits the emission of fuel fumes into the environment.
Current fuel delivery systems provide fuel to a vehicle""s combustion chambers through a fuel rail that channels fuel from the fuel tank to fuel injectors above the chambers. While many fuel rails are constructed of metal, more recently, manufacturers have commenced using plastic fuel rails to distribute fuel to the injectors. Plastic fuel rails are lighter and casier to recycle with other plastic components associated with the vehicle engine. Plastic fuel rails, however, are porous and consequently permit fumes or vapor from the liquid fuel to permeate into the environment. Higher emission standards make the emission of fumes through the rail a source of concern for manufacturers using plastic fuel rails.
Manufacturers have attempted to address this environmental concern by using various coatings to prevent fumes from entering the environment. For the most part, these coatings have been ineffective or extremely expensive to employ.
A need therefore exists for a fuel delivery system that limits the exhaust of fumes into the environment while still permitting manufacturers to employ plastic fuel distribution systems.
The invention comprises a fuel delivery system. The system has a fuel rail or conduit that has a wall formed of plastic. A gas rail or conduit surrounds this wall such that any gas vapor permeating through the fuel conduit passes into the gas conduit. Hence, while vapor may pass through the fuel conduit into the gas conduit, the remaining fuel continues to the fuel injector and ultimately the vehicle engine. In this way, the fuel conduit transports fuel to a vehicle""s combustion chamber without significant environmental emissions.
The gas conduit surrounds the fuel conduit. Essentially, some way of directing the vapor from the gas conduit to a source such as the engine may be utilized. Much work has been done in recent years in capturing and processing vapor, and any of the ways of moving the vapor may be utilized with this invention. Particular embodiments will be disclosed. However, other methods may also be utilized.
The outer wall of the gas conduit is also preferably formed of plastic. Thus, the outer wall of the gas conduit also will potentially allow permeation of fuel vapor. However, by maintaining a lower pressure compared to atmosphere in the gas conduit, the likelihood of significant vapor permeation will be reduced or eliminated.
In essence, the fuel delivery system communicates a fuel through the fuel conduit. Any vapor that passes through a wall of the fuel conduit passes into a gas conduit. Rather than permitting any vapor to enter the environment, the invention recirculates the vapor to the vehicle engine or otherwise processes the vapor.